It seems the Warden is no longer part of the big picture, as Cortana took command and now Master Chief faces a big decision.
You play as Master Chief alongside Blue Team. Begin by moving along a hallway and passing through a pair of doors leading to an open area. Take care of the enemies in this location, including Crawlers and a few other Prometheans, then make your way towards a bright light at the end.
From there, you’ll be able to go to a nearby Forerunner console and see a piece of Intel right next to it. Pick it up, then go through the doorway, where you’ll be on a platform that will move its way forward. Here, you’ll deal with a few more Prometheans before getting to the next part of the stage. Kill these enemies, then keep going down the path. Be sure to keep an eye open for Turret gunfire from above, right by the top door.
You’ll go through this metallic-like hallway and deal with the Eternal Warden and a few enemies. He’ll hold back, so you don’t need to deal with him yet. Take care of the smaller foes he throws at you and move on.
Another platform will take you to a higher part of the stage. You’ll want to make note of the metal panels, as they’ll provide cover from both the Turrets and the enemies (namely Knights and Soldiers) that come at you. Use it properly and clean them out, but be sure to concentrate some fire on the Turrets as well.
You’ll reach one final section where you’ll have to deal with both Turrets and a trio of Wardens. Tell Blue Team to concentrate their fire on each of the Wardens, and eventually you’ll bring them down, along with the Turrets.
Once that’s done, go across a walkway and light bridge to come face to face with Cortana, where Master Chief will need to make his decision via a cut scene. This concludes mission 14.
Proceed to Mission 15: Guardians, or head to the free Halo 5: Guardians Walkthrough and Guide. For in-depth strategies and secrets, check out the Official eGuide and Halo 5: Guardians Collector’s Edition Strategy Guide.